<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			
			//1.变量名要符合规范
			var a =123
			var _name = "majiaqi"
			
			//2.变量类型是由赋值决定
			var b = "123"
			console.log(b)
			console.log(typeof b)
			b=123;
			console.log(b)
			console.log(typeof b)
			
			//var也可以不写
			c="hello"
			console.log(c)
			console.log(typeof c)
			
			//没有声明，没有赋值，直接用会报错
			console.log(d)
			
		</script>
	</body>
</html>
